Explorations of Gravel Mining, the Antarctic Shelf and "Natural" Cleansers

What are the environmental impacts of gravel extraction?

Kristina Hayward Berkshire, UK

Gravel extraction, often in stream beds, is big business in the United States and elsewhere, and there's a definite environmental cost. Gravel is used to help build patios, parking lots, roads and building construction. A geologic report by Ohio's Department of Natural Resources (DNR) recorded a combined sales total of over 57 million tons of sand and gravel for that state alone in 1997.

Extraction of gravel in streams and rivers results in sediment-related pollution and a disturbance of natural hydraulic patterns. Carl Mount, senior environmental protection specialist of the Division of Minerals and Geology, Colorado DNR, notes that although the state has 75 in-stream extraction operations, “It's not being done as much. The river is a hassle to deal with—and it's expensive.” He explains that most operations now mine the floodplains next to streams or “build a diversion so the stream flows around the area they're mining”—a practice that is in itself disruptive. Peter Dobbins, director of Friends of the Garcia River, says his California-based group successfully fought off a mining proposal because “in-stream gravel extraction ruins water quality and destroys habitat for fish, reptiles and birds.”

CONTACTS

Friends of the Garcia RiverTel: (707) 882-3086

United States Geological Service

What are the implications of the large iceberg (I heard the size of Jamaica) that disconnected from Antarctica?

Gaertner Olivier Brussels, Belgium

According to The National Snow and Ice Data Center (NSIDC), the ice sheets of Antarctica are huge, floating platforms of ice that are grounded by the Antarctic continent and islands in the region. Snow, glaciers and ice flows feed these large ice sheets in the colder months. In warmer periods, surface melting and the breaking off (calving) of icebergs decrease the mass.

The iceberg in question was named “B-15” by the National Ice Center, a governmental organization that tracks icebergs for vessel safety. B-15, which is 170 miles long and 25 miles wide, calved from the Ross Ice Shelf on March 30; its mass converts to about 3.2 trillion tons of fresh water.

This vast amount of water has a surprisingly neutral effect on sea levels. Dr. Ted Scambos, a research associate scientist at the University of Colorado, explains, “Since an iceberg floats in ocean water, and much of it is below the surface, it is already displacing the same volume of water it will contribute when it eventually melts.” He also contends that this calving does not in itself signal any catastrophic global warming trend. “Large icebergs like the B-15 calve off on a fairly regular basis from the larger ice shelves in Antarctica,” he says. “This is a part of their normal evolution.” The ice sheets, glaciers and snow that are experiencing warming effects and not currently displacing water are the ones to worry about, Scambos says.

CONTACTS

National Snow and Ice Data Center Tel: (303) 492-6199

The National Ice Center Tel: (301) 457-5303

Are “environmentally safe” household cleaners really better for the health of aquatic life?

Barbara Mounts Brattlebobro, VT

“The average household today contains more chemicals than the average chemical laboratory of 100 years ago,” says Michael Haire of the Maryland Department of the Environment. Where do all those chemicals end up when poured or rinsed down our drains? “They come to plants like ours,” answers Fred Treffeisen, a wastewater treatment plant employee in Connecticut. All the water received at the treatment facility goes through a “biological process” involving microorganisms. What isn't eliminated in this phase may settle out at the bottom as “sludge.” This by-product is taken to an incinerator, and the leftover ash, often heavy metals, is eventually taken to a landfill. The treated water is released back into our streams and oceans.

In general, natural cleaners are derived from renewable plant materials, instead of petrochemicals, and are inherently more friendly to aquatic life. Natural cleaners can be labeled “eco-friendly,” “all natural,” “biodegradable,” “non-toxic” and “environmentally safe.” Lynn Marie Bower, author of The Healthy Household, warns, “Often, the use of these terms is not legally regulated,” and so the impact of “natural” cleaners can vary. Steve Rayburn, a chemist at North Carolina's Guilford Laboratories, points out that people often believe biodegradable means non-toxic. But, he says, “There is a carcinogenic substance named butyl cellosolve that is highly biodegradable and very toxic.” To complicate things further, natural products also decay back into the environment at varying rates.

CONTACTS

Earthsafe and Wellness Technologies Tel: (888) 209-2808

The National Library of Medicine's TOXNET database can be searched for specific cleaner ingredients.

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